1. Field of the Invention
The present invention relates to a display apparatus.
2. Description of the Related Art
It is expected that the organic electroluminescent (EL) display apparatus, as a display apparatus, shall replace currently widespread liquid crystal display apparatus, and the development of the organic EL display apparatus for practical use is advancing. In particular, active-matrix type organic electroluminescent display apparatus (hereinafter referred to simply as “organic EL display apparatus” also) equipped with thin film transistors (hereinafter simply abbreviated as “TFT”) that serve as switching elements are considered to play a leading role as next-generation flat panel display apparatus.
As shown in FIG. 7, an organic EL display apparatus has display pixels disposed in a matrix in a display area 200 on an insulating substrate 10. Moreover, as will be described later in detail in preferred embodiments, each display pixel includes an organic EL element which is laminated in order with an anode, organic material and a cathode, and a TFT which drives the organic EL element. Also, provided in the periphery of the display area 200 are a scanning driver 210 that outputs scanning signals and a luminance data driver 220 that outputs luminance data to be set in respective display pixels. Furthermore, various signals to be supplied to the organic EL element are inputted from a first terminal 100 and second terminals 100a disposed on one end of the periphery of the display area 200.
A wiring structure which is utilized for the input of signals to display pixels of such a display apparatus is disclosed in Japanese Patent Application Laid-Open No. 2001-282136. FIGS. 8A and 8B illustrate examples of such a wiring structure. FIG. 8A is a cross-sectional view along line A—A in FIG. 7, showing the vicinity of terminal regions that supply voltage to the cathode.
As shown in FIG. 8A, the first terminal 100 and second terminals 100a, which are all made of aluminum, are formed on the insulating substrate 10. The first terminal 100 feeds voltage to a cathode 67, and the second terminals 100a function as signal input terminals for parts other than the cathode 67.
An interlayer insulating film 15 is disposed between terminals, and an ITO (Indium Tin Oxide) film 61a is laminated on each of the aluminum terminals. This ITO film 61a is placed simultaneously with the formation of the anode of the organic EL element. The ITO film 61a is further laminated with a cathode material which connects the ITO film 61a to the cathode 67.
Here, the ITO film 61a is formed to prevent the aluminum terminals from being etched when the anodes of organic EL elements are etched in a manner of islands for the respective display pixels. This ITO film 61a thus protects the first terminal 100 and second terminals 100a from being etched.
Moreover, the structure shown in FIG. 8B is a structure that features a lowered contact resistance by providing a refractory metal 70 between the ITO film 61a and the terminal 100 of the wiring structure shown in FIG. 8A. In this structure, the refractory metal 70 is laminated on the first terminal 100 by a sputtering or like method after the formation of the first terminal 100.
It is to be noted that the organic EL display apparatus, whose optical elements are of the current-driven type, requires higher reliability for their wiring than the display apparatus such as liquid crystal display apparatus whose optical elements are of the voltage-driven type.
While reduction in contact resistance is realized by the conventional structure as shown in FIG. 8B, there are still demands for materials and wiring structures that excel in resistance to electromigration or stressmigration.